To receive high-voltage electric power through an overhead contact line and supply the electric power to respective devices of a railcar, the railcar includes on an upstream side a plurality of high voltage devices, such as a power collector (pantograph), a vacuum circuit breaker (VCB), a lightning arrester (arrester), and a transformer. Then, a high voltage device system is constituted by these high voltage devices, high-voltage cables interposed among the high voltage devices, a joint device configured to connect the high-voltage cables with one another, and the like.
As conventional joint devices, two types that are a straight joint device and a Y branch joint device are known. The straight joint device connects two high-voltage cables with each other in a straight manner whereas the Y branch joint device connects three high-voltage cables with one another.
FIG. 7 shows the vicinity of a power collector arranged on a roof of a railcar and using a Y branch joint device. In FIG. 7, a collector shoe and arm portion of the power collector are omitted. Two high-voltage cables 270 respectively extend from front and rear sides of a power collector 230 in a railcar longitudinal direction. One of the high-voltage cables 270 is connected to a vacuum circuit breaker arranged under a floor of a car, and the other high-voltage cable 270 is connected to a receiving opening 252a of a Y branch joint device 252. In the Y branch joint device 252, the high-voltage cable 270 branches into two cables. One of the two cables is connected to a receiving opening 252b of the Y branch joint device 252 and extends toward a front-side car, and the other cable is connected to a receiving opening 252c of the Y branch joint device 252 and extends toward a rear-side car. Thus, the electric power is supplied to the respective ears.
In a case where the high-voltage cable 270 is connected to the Y branch joint device 252, a so-called prefabricated joint (see PTL 2) is adopted in the high voltage device system of the railcar, the prefabricated joint being configured such that: a rubber stress-relief cone (not shown) arranged at a terminal of the high-voltage cable 270 is inserted into the receiving opening of the Y branch joint device 252 which is made of epoxy resin and the like and in which an internal conductor (not shown) is embedded; and the stress-relief cone is pressed against the receiving opening by a compression unit (not shown).
PTL 1 discloses an electric power cable connecting device using a conventional joint device. FIG. 2 of PTL 1 discloses a configuration corresponding to a straight joint device to which the prefabricated joint is applied and which is for use in the railcars.
PTL 2 discloses a prefabricated joint. FIGS. 6 and 8 of PTL 2 disclose a configuration corresponding to a Y branch joint device to which the prefabricated joint is applied.